diff --git a/.circleci/config.yml b/.circleci/config.yml
index 578043e864e6..404054466e1a 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -104,17 +104,6 @@ jobs:
       - store_test_results:
           path: reports/junit
 
-  test-browser:
-    working_directory: ~/jest
-    docker:
-      - image: circleci/node:12-browsers
-    steps:
-      - checkout
-      - restore-cache: *restore-cache
-      - run: *install
-      - save-cache: *save-cache
-      - run: yarn test-ci-es5-build-in-browser
-
   test-or-deploy-website:
     working_directory: ~/jest
     docker:
@@ -140,6 +129,5 @@ workflows:
       - test-node-13
       - test-node-14 # current
       - test-jest-circus
-      - test-browser
       - test-or-deploy-website:
           filters: *filter-ignore-gh-pages
diff --git a/.eslintignore b/.eslintignore
index 05311c4695d6..be8072a6a850 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -3,7 +3,6 @@
 bin/
 flow-typed/**
 packages/*/build/**
-packages/*/build-es5/**
 packages/jest-diff/src/cleanupSemantic.ts
 website/blog
 website/build
diff --git a/.eslintrc.js b/.eslintrc.js
index 3594b3b18ec6..b72d563d7295 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -95,7 +95,6 @@ module.exports = {
       files: [
         'packages/jest-jasmine2/src/jasmine/**/*',
         'packages/expect/src/jasmineUtils.ts',
-        'e2e/browser-support/browserTest.js',
         '**/vendor/**/*',
       ],
       rules: {
diff --git a/.github/workflows/nodejs.yml b/.github/workflows/nodejs.yml
index 78c1927a0e6f..5df30a9d3bc7 100644
--- a/.github/workflows/nodejs.yml
+++ b/.github/workflows/nodejs.yml
@@ -45,8 +45,6 @@ jobs:
         run: yarn verify-old-ts
       - name: run eslint
         run: yarn lint
-      - name: run eslint on browser builds
-        run: yarn lint-es5-build
       - name: run prettier
         run: yarn lint:prettier:ci
       - name: check copyright headers
diff --git a/.gitignore b/.gitignore
index 36a8de27bd81..c6b727d6dfa1 100644
--- a/.gitignore
+++ b/.gitignore
@@ -17,7 +17,6 @@
 /node_modules
 
 /packages/*/build/
-/packages/*/build-es5/
 /packages/*/coverage/
 /packages/*/node_modules/
 /packages/*/package-lock.json
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 38b9b4387f3f..d738e9188d90 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,8 @@
 
 ### Chore & Maintenance
 
+- `[expect, jest-mock, pretty-format]` [**BREAKING**] Remove `build-es5` from package ([#9945](https://github.com/facebook/jest/pull/9945))
+
 ### Performance
 
 ## 25.5.3
diff --git a/e2e/browser-support/browserTest.js b/e2e/browser-support/browserTest.js
deleted file mode 100644
index 2fbeae3d08c0..000000000000
--- a/e2e/browser-support/browserTest.js
+++ /dev/null
@@ -1,28 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-/* eslint-disable */
-var expect = require('expect');
-var mock = require('jest-mock');
-var prettyFormat = require('pretty-format');
-
-describe('es5 builds in browser', function() {
-  it('runs assertions', function() {
-    expect(1).toBe(1);
-  });
-
-  it('runs mocks', function() {
-    var someMockFunction = mock.fn();
-    expect(someMockFunction).not.toHaveBeenCalled();
-    someMockFunction();
-    expect(someMockFunction).toHaveBeenCalledTimes(1);
-  });
-
-  it('pretty formats a string', function() {
-    expect(prettyFormat('obj')).toBe('"obj"');
-  });
-});
diff --git a/jest.config.js b/jest.config.js
index cb189da42604..18ad91a82b6d 100644
--- a/jest.config.js
+++ b/jest.config.js
@@ -23,7 +23,6 @@ module.exports = {
   modulePathIgnorePatterns: [
     'examples/.*',
     'packages/.*/build',
-    'packages/.*/build-es5',
     'packages/jest-runtime/src/__tests__/test_root.*',
     'website/.*',
     'e2e/runtime-internal-module-registry/__mocks__',
@@ -44,7 +43,6 @@ module.exports = {
     '/e2e/global-teardown',
     '\\.snap$',
     '/packages/.*/build',
-    '/packages/.*/build-es5',
     '/packages/.*/src/__tests__/setPrettyPrint.ts',
     '/packages/jest-core/src/__tests__/test_root',
     '/packages/jest-core/src/__tests__/__fixtures__/',
diff --git a/karma.conf.js b/karma.conf.js
deleted file mode 100644
index 61e032d44fa7..000000000000
--- a/karma.conf.js
+++ /dev/null
@@ -1,25 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-module.exports = config => {
-  config.set({
-    browsers: ['ChromeHeadless'],
-    files: ['e2e/browser-support/browserTest.js'],
-    frameworks: ['mocha'],
-    preprocessors: {
-      'e2e/browser-support/browserTest.js': ['webpack'],
-    },
-    webpack: {
-      mode: 'development',
-    },
-    webpackMiddleware: {
-      // webpack-dev-middleware configuration
-      // i. e.
-      stats: 'errors-only',
-    },
-  });
-};
diff --git a/package.json b/package.json
index 338d2679d898..e560e0355b7e 100644
--- a/package.json
+++ b/package.json
@@ -59,10 +59,6 @@
     "jest-snapshot-serializer-raw": "^1.1.0",
     "jest-watch-typeahead": "^0.5.0",
     "jquery": "^3.2.1",
-    "karma": "^4.0.1",
-    "karma-chrome-launcher": "^3.0.0",
-    "karma-mocha": "^1.3.0",
-    "karma-webpack": "^4.0.2",
     "lerna": "^3.20.2",
     "make-dir": "^3.0.0",
     "micromatch": "^4.0.2",
@@ -82,7 +78,6 @@
     "tempy": "~0.3.0",
     "throat": "^5.0.0",
     "typescript": "^3.8.2",
-    "webpack": "^4.28.4",
     "which": "^2.0.1"
   },
   "scripts": {
@@ -96,14 +91,12 @@
     "jest": "node ./packages/jest-cli/bin/jest.js",
     "jest-coverage": "yarn jest --coverage",
     "lint": "eslint . --cache --ext js,jsx,ts,tsx,md",
-    "lint-es5-build": "eslint --no-eslintrc --no-ignore --env=browser packages/*/build-es5",
     "lint:prettier": "prettier '**/*.{md,yml,yaml}' 'website/static/**/*.{css,js}' --write --ignore-path .gitignore",
     "lint:prettier:ci": "prettier '**/*.{md,yml,yaml}' 'website/static/**/*.{css,js}' --check --ignore-path .gitignore",
     "postinstall": "opencollective postinstall && yarn build",
     "install-no-ts-build": "node ./scripts/remove-postinstall && yarn --no-progress --frozen-lockfile && node ./scripts/build",
     "remove-prettier-dep": "node ./scripts/remove-prettier-dep",
     "publish": "yarn build-clean && yarn build && lerna publish --silent",
-    "test-ci-es5-build-in-browser": "karma start --single-run",
     "test-ci": "yarn jest-coverage --color -i --config jest.config.ci.js && yarn test-leak && node ./scripts/mapCoverage.js && codecov",
     "test-ci-partial": "yarn jest --color -i --config jest.config.ci.js",
     "test-pretty-format-perf": "node packages/pretty-format/perf/test.js",
diff --git a/packages/expect/package.json b/packages/expect/package.json
index df859e2e4715..18101b026061 100644
--- a/packages/expect/package.json
+++ b/packages/expect/package.json
@@ -16,7 +16,6 @@
       ]
     }
   },
-  "browser": "build-es5/index.js",
   "dependencies": {
     "@jest/types": "^25.5.0",
     "ansi-styles": "^4.0.0",
diff --git a/packages/jest-mock/package.json b/packages/jest-mock/package.json
index 775cc56c409d..33e5455da8ac 100644
--- a/packages/jest-mock/package.json
+++ b/packages/jest-mock/package.json
@@ -25,7 +25,6 @@
       ]
     }
   },
-  "browser": "build-es5/index.js",
   "publishConfig": {
     "access": "public"
   },
diff --git a/packages/pretty-format/package.json b/packages/pretty-format/package.json
index dedbfab6721a..66ea7d8b2c16 100644
--- a/packages/pretty-format/package.json
+++ b/packages/pretty-format/package.json
@@ -17,7 +17,6 @@
       ]
     }
   },
-  "browser": "build-es5/index.js",
   "author": "James Kyle <me@thejameskyle.com>",
   "dependencies": {
     "@jest/types": "^25.5.0",
diff --git a/scripts/browserBuild.js b/scripts/browserBuild.js
deleted file mode 100644
index 6e35147a9dd6..000000000000
--- a/scripts/browserBuild.js
+++ /dev/null
@@ -1,87 +0,0 @@
-/**
- * Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-'use strict';
-
-const path = require('path');
-const webpack = require('webpack');
-const camelCase = require('camelcase');
-const rimraf = require('rimraf');
-
-const transformOptions = require('../babel.config.js');
-
-const babelEs5Options = {
-  // Dont load other config files
-  babelrc: false,
-  configFile: false,
-  overrides: transformOptions.overrides,
-  plugins: ['@babel/plugin-transform-strict-mode'],
-  presets: [
-    [
-      '@babel/preset-env',
-      {
-        // Required for Webpack
-        modules: 'cjs',
-        shippedProposals: true,
-        // Target ES5
-        targets: 'IE 11',
-      },
-    ],
-  ],
-};
-
-function browserBuild(pkgName, entryPath, destination) {
-  rimraf.sync(destination);
-
-  return new Promise((resolve, reject) => {
-    webpack(
-      /* eslint-disable sort-keys */
-      {
-        mode: 'development',
-        devtool: 'source-map',
-        entry: entryPath,
-        output: {
-          path: path.dirname(destination),
-          library: camelCase(pkgName),
-          libraryTarget: 'umd',
-          filename: path.basename(destination),
-        },
-        module: {
-          rules: [
-            {
-              test: /\.[jt]sx?$/,
-              loader: require.resolve('babel-loader'),
-              options: babelEs5Options,
-            },
-          ],
-        },
-        resolve: {
-          alias: {
-            chalk: path.resolve(
-              __dirname,
-              '../packages/expect/build/fakeChalk.js',
-            ),
-            'graceful-fs': 'fs',
-          },
-          extensions: ['.js', '.json', '.ts'],
-        },
-        node: {
-          fs: 'empty',
-        },
-      },
-      /* eslint-enable */
-      (err, stats) => {
-        if (err || stats.hasErrors()) {
-          reject(err || stats.toString());
-          return;
-        }
-        resolve(stats);
-      },
-    );
-  });
-}
-
-module.exports = browserBuild;
diff --git a/scripts/build.js b/scripts/build.js
index 7c5e0f5c3ba7..d6d718cbe322 100644
--- a/scripts/build.js
+++ b/scripts/build.js
@@ -30,11 +30,9 @@ const chalk = require('chalk');
 const micromatch = require('micromatch');
 const prettier = require('prettier');
 const {getPackages, adjustToTerminalWidth, OK} = require('./buildUtils');
-const browserBuild = require('./browserBuild');
 
 const SRC_DIR = 'src';
 const BUILD_DIR = 'build';
-const BUILD_ES5_DIR = 'build-es5';
 const JS_FILES_PATTERN = '**/*.js';
 const TS_FILES_PATTERN = '**/*.ts';
 const IGNORE_PATTERN = '**/__{tests,mocks}__/**';
@@ -72,39 +70,6 @@ function buildNodePackage(p) {
   process.stdout.write(`${OK}\n`);
 }
 
-function buildBrowserPackage(p) {
-  const srcDir = path.resolve(p, SRC_DIR);
-  const pkgJsonPath = path.resolve(p, 'package.json');
-
-  if (!fs.existsSync(pkgJsonPath)) {
-    return;
-  }
-
-  const browser = require(pkgJsonPath).browser;
-  if (browser) {
-    if (browser.indexOf(BUILD_ES5_DIR) !== 0) {
-      throw new Error(
-        `browser field for ${pkgJsonPath} should start with "${BUILD_ES5_DIR}"`,
-      );
-    }
-    let indexFile = path.resolve(srcDir, 'index.js');
-
-    if (!fs.existsSync(indexFile)) {
-      indexFile = indexFile.replace(/\.js$/, '.ts');
-    }
-
-    browserBuild(p.split('/').pop(), indexFile, path.resolve(p, browser))
-      .then(() => {
-        process.stdout.write(adjustToTerminalWidth(`${path.basename(p)}\n`));
-        process.stdout.write(`${OK}\n`);
-      })
-      .catch(e => {
-        console.error(e);
-        process.exit(1);
-      });
-  }
-}
-
 function buildFile(file, silent) {
   const destPath = getBuildPath(file, BUILD_DIR);
 
@@ -187,8 +152,4 @@ if (files.length) {
   const packages = getPackages();
   process.stdout.write(chalk.inverse(' Building packages \n'));
   packages.forEach(buildNodePackage);
-  process.stdout.write('\n');
-
-  process.stdout.write(chalk.inverse(' Building browser packages \n'));
-  packages.forEach(buildBrowserPackage);
 }
diff --git a/tsconfig.json b/tsconfig.json
index a513c83fe2c2..b1d9bfdd5414 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -29,7 +29,6 @@
     ".yarn/releases/*",
     "**/__tests__/**/*",
     "**/__mocks__/**/*",
-    "**/build/**/*",
-    "**/build-es5/**/*"
+    "**/build/**/*"
   ]
 }